Brushless generators are conventionally formed of a permanent magnet generator, an exciter, and a main generator. Typically, relatively low levels of power are generated by the permanent magnet generator which is made up of a permanent magnet field carried by the generator rotor and which induces electrical energy in a permanent magnet generator output winding. The power from this winding is rectified and subjected to known control parameters before being fed to a stationary field winding of the exciter. The exciter also includes an output winding carried by the rotor and as the same rotates within the magnetic field generated by the exciter field winding, electrial energy is induced in the exciter output winding. The current will be alernating current and typically will be three phase alternating current.
In any event, the resulting electrical energy is rectified by means of a rectifier carried by the rotor and rotating therewith and then supplied to the main field winding of the main generator. The main field winding is, of course, carried by the rotor and when energized with direct current, and when rotated provides a rotating magnetic field which in turn induces an alternating current in a stationary, main armature output winding. Power thus generated may be taken from the stationary main armature output winding to a point of use and it will be appreciated that the entire system is operative without any need for the presence of brushes.
These systems work very well for their intended purpose which most frequently but not always, is in aircraft power generating applications. The generators are coupled mechanically to the aircraft engine. In the case of jet engines, the coupling is to the engine gear box with the generating system being housed in the same cowling as the engine itself.
It is of course desirable in aircraft applications to minimize weight. In the case of brushless generators having a relatively long axial length, because such generators are typically mounted to the engine gear box at only one end of the generator, such generators result in the presence of a relatively large, so-called "overhung" moment. In order to support such a generator, the gear box must be made proportionately stronger than would be the case for a generator having a lesser overhung moment; and that reinforcement will most frequently require the presence of additional, undesirable weight. In addition, aircraft applications require that close heed be paid to aerodynamic consideration. These considerations may dictate location of aircraft components in areas where space is at a premium or else an aerodynamic penalty may be felt.
The present invention is directed to overcoming one or more of the above problems.